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The present investigation was conducted at Vittal, Karnataka, India during December 1996 to May 2006 to evaluate the effect of four fertigation levels (25, 50, 75 and 100% of recommended fertilizer dose, 100:18:117 g N:P:K palm-1 year-1), three frequencies of fertigation (10, 20 and 30 days) and two controls (control 1, i.e., drip irrigation without fertilizer application and control 2, i.e., drip with 100% NPK soil application) on productivity and resource use efficiency of arecanut. The experiment was laid out in RBD incorporating factorial component (4 × 3 + 2) in 2-year-old arecanut plantation. Pooled analysis of 4-year data indicated the significant influence of both fertilizer dose and frequency of fertigation on kernel yield of arecanut. Among fertigation levels, the kernel yield was significantly higher in 75% NPK fertigation, i.e., 75:13.5:87.7 g N, P, K application per year (3721 kg ha-1) than in other levels (3083�3121 kg ha-1). The yields observed in 10 (3431 kg ha-1) and 20 days frequencies (3382 kg ha-1) were at par and significantly superior to monthly fertigation frequency (2952 kg ha-1). Fertigation of 75% NPK at 10 days frequency registered maximum yield (4017 kg ha-1), which was closely followed by fertigation of 75% NPK at 20 days frequency (3924 kg ha-1) and fertigation of 100% NPK at 20 days frequency (3579 kg ha-1). The yield increase with 75% NPK fertigated at 10 days interval was 100% over control 1 (2008 kg ha-1). Different fertigation levels registered higher dry matter partitioning to kernel, i.e., 6.7�7.4% of the total biomass than no fertilizer application (5.6%). A significant correlation between biomass accumulation in different parts and fertigation levels indicates the importance of efficient application of nutrients at correct time and quantity. Leaf water potential increased significantly with increase in frequency of fertigation from 10 to 30 days interval. A strong linear correlation (R2 = 0.914) was observed between fertigation level and total root biomass. The root biomass increased considerably from 3.23 (no fertilizer) to 7.99 kg per palm (75% NPK). Significant relation between root biomass and organic carbon content in soil based on polynomial regression (R2 = 0.769) was also noticed. Water use efficiency (WUE) was significantly superior at 75% NPK applied at 10 days interval over 100% NPK applied at same interval. However, it was at par with 75 and 100% NPK applied at 20 days interval Agronomic nutrient use efficiency (ANUE) was significantly higher at 25% NPK (14.9 kg kernel produced per kg nutrient applied). Fertigation up to 75% NPK provided a higher ANUE than the combination of drip irrigation and soil application of 100% NPK indicating greater production at lesser application rates. The 11-year study indicated that adoption of fertigation not only increases productivity, but also ensures higher efficiency of the two most critical inputs, i.e., water and nutrients in crop production
